This invention relates to pipe couplings and more particularly to a rigid tube connection sealing apparatus.
In the past, various structures have been proposed for jointing pipes. One such annular joint structure includes an annular ring of resilient material having a T-shaped cross-section. A metal ring centering member also having a T-shaped cross-section supports a pair of opposing spring sheet parts; these elements are embedded in the annular ring. When the pipe ends are forced together the resilient material of the annular ring seals the ends of the pipes and forces the metal spring members together so that axially extending portions thereof are urged radially outwardly against the inner surface of the two pipe ends to ensure a complete seal between the joint itself and the two pipe ends. Those persons desiring more information concerning this structure are referred to U.S. Pat. No. 4,269,437, issued May 26, 1981 to Shaw et al. Other pipe coupling structures are shown in U.S. Pat. No. 4,568,113 issued Feb. 4, 1986, to Axford et al. for a "Pipe Connection"; U.S. Pat. No. 3,100,656 issued Aug. 13, 1963 to M. D. MacArthur for a "Synthetic Resin Seal Ring In Tubing Joint For Plastic Coated Tubing" ; U.S. Pat. No. 3,266,821 issued Aug. 16, 1966 to W. J. Safford for a "Sealed Pipe Coupling"; U.S. Pat. No. 2,793,833, issued May 28, 1957 to B. A. Main, Jr. for a "Flexible Joint For Rigid Tube"; U.S. Pat. No. 4,431,845, issued Nov. 8, 1983 to Lawrence for "Pipe Couplings"; U.S. Pat. No. 4,230,157, issued Oct. 28, 1980 to Larsen et al. for a "Pipe Having An End Portion, The Inner Wall Of Which Is Provided With A Circumferential Groove, In Which A Sealing Means Is Mounted And A Pipe Joint consisting Of This Pipe And A Spigot End Of A Second Pipe Inserted Therein"; and U.S. Pat. No. 3,989,285 issued Nov. 2, 1976 to Yancey for a "Compatible Vacuum Seal".
The problems confronting the pipe coupling art relate to leakage and pipe corrosion. In addition in connected pipes, through which hardware items are passed, such as, for example, oil well drilling bits, seals having inside protrusions are damaged when hit by the hardware thereby causing leakage. In 8-Round threaded pipes used in many oil and gas wells having a sour gas environment or high pressure or both, leakage can become a problem. By design, 8-round threaded pipes have an inherent helical leak path in the threads that must be blocked; a pipe dopant has been used to seal off this leakage path. Dopant dryout can result in leakage through the thread gaps. Further, in systems having significant gaps between pipe ends, gas turbulence induces corrosion and washout of thread which results in leakage and failure of the pipe.